Nice source! Thank you kindly.

Planting trees and shrubs close by a condenser may actually reduce system efficiency due to impedance of effective air movement. We conclude that any savings produced by localized AC condenser shading are quite modest (<3%) and that the risk of interrupting airflow to the condenser may outweigh shading considerations. The preferred strategy may be a long-term one: locating AC condensers in an unobstructed location on the shaded north side of buildings and depending on extensive site and neighborhood-level landscaping to lower localized air temperatures.

Tracks with the gut feeling. Shade will only marginally improve efficiency but constricting flow definitely hurts. Units are best installed on the North/Northeast sides of houses in the northern hemisphere.